Karyology and Phylogenetic Relationships of Phleum pratense, P. commutatum, and P. bertolonii1

Abstract

Two polyploid and one diploid timothy species are found in North America: Phleum pratense L. (2n = 42), P. alpinum var. commutatum (Gaud.) Koch (2n = 28), and P. bertolonii DC. (2n = 14). Karyotypes and photomicrographs of P. pratense and P. commutatum Gaud. and a photomicrograph of P. bertolonii are presented.Chromosome arm‐length measurements, arm‐length ratios, and other detailed observations showed that P. pratense has three pairs of short acrocentric chromosomes, three pairs of long submetacentric chromosomes, and three pairs of equisized chromosomes with satellites. P. commutatum has two pairs of small acrocentric chromosomes, and one pair of long metacentrics, a slightly shorter pair of submetacentrics, and a pair of satellited chromosomes. This and other data obtained from photomicrographs of cells of commutatum plants from Alaska and Wyoming suggest that P. commutatum has one genome in common with P. pratense. All indications are that P. pratense is an autohexaploid, and P. commutatum is an allotetraploid. The P. bertolonii genome is karyotypically similar to the P. pratense genome.